Biomaterial Database

Burst kinetics of single calcium-activated potassium channels in cultured rat muscle. 1983

K L Magleby, and B S Pallotta

Burst kinetics of single Ca-activated K channels in excised patches of surface membrane from cultured rat muscle were studied using the patch-clamp technique. Channel activity was separated into bursts using a calculated gap derived from the distribution of shut intervals. Shut intervals greater than the calculated gap were taken as gaps between bursts. The distribution of burst duration was described as the sum of two exponentials with mean durations of about 0.8 and 24 msec (1 microM-Cai, + 20 mV), suggesting two classes of bursts (short and long). The composition of short and long bursts was determined from comparisons of the distributions of open intervals, unit bursts (bursts of single openings), and openings/burst. Short bursts consisted mainly of single openings to the open channel state of short mean lifetime. Long bursts consisted of one or more openings to the (compound) open-channel state of long mean lifetime, plus, in fewer than 70% of the long bursts, one or more openings to the short open-channel state. The frequency of occurrence of bursts from each class first increased and then decreased with increasing [Ca]i, with the number of long bursts increasing at a greater rate than the number of short bursts. The number of openings/short burst was relatively independent of [Ca]i, while the number of openings/long burst increased, often more than linearly, with increasing [Ca]i. This increase arose almost entirely from an increase in openings to the long open state. These results suggest that openings to the long open state typically require the binding of three or more Ca ions, and openings to the short open state typically require the binding of at least one Ca ion. This is the case whether the openings occur in isolation as bursts of single openings or in bursts composed of both types of openings. An obvious burst of channel activity would occur when the channel opens and closes several times without losing all its bound Ca. The power relationship between [Ca]i and the percentage of time spent in the open state is accounted for in terms of the effects of [Ca]i upon mean channel open time, openings/burst, and burst rate. A model is presented that describes quantitatively many features of the burst kinetics of the Ca-activated K channel for constant [Ca]i.

UI	MeSH Term	Description	Entries
D007473	Ion Channels	Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.	Membrane Channels,Ion Channel,Ionic Channel,Ionic Channels,Membrane Channel,Channel, Ion,Channel, Ionic,Channel, Membrane,Channels, Ion,Channels, Ionic,Channels, Membrane
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D051381	Rats	The common name for the genus Rattus.	Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus